Electric guitars and other modern stringed instruments produce signals that are passed through a chain of electronic musical effect generators before being amplified and passed to a speaker or headphone system. These electronic effect generators alter the final output sound by modifying properties such as the frequency response, overall amplitude, envelope characteristics, echo, reverberation and distortion.
Prior art devices provide control over these properties with knobs, hand or foot switches, foot pedals and in some cases by preset signal levels. It can be appreciated, however, that these devices for changing characteristics of the sound signal have several disadvantages or limitations.
First, in the case of simple hand and foot switches, the musician can only turn the effect on or off. There is no way control the amount of the effect. To solve this, many of these devices incorporate dials and knobs so the guitarist can adjust the amount of a given effect. However, a musician using these dials and knobs must remove his or her hands from the strings of the guitar to adjust the amount of the effect. This causes an unacceptable disruption in the playing of the instrument and thereby limits the usefulness of these devices and the achievement of the desired sound effect.
Dynamic foot peddle effect generators have been developed, such as those illustrated in U.S. Pat. No. 3,530,224, which are operated by foot and change the parameters of the effect dynamically as the pedal is actuated back and forth. These types of foot peddles are quite effective in not interrupting the playing of the instrument, but are limited by the lack of sensitivity and speed of actuation. Moreover, they limit the musician to a single fixed position on the stage.
U.S. Pat. No. 4,503,746 addresses the musician mobility issue by using the force the musician applies to the shoulder strap as a means for controlling musical effect parameters. Although successful in decoupling the musician from a certain point on a stage, this configuration lacks the sensitivity and speed of actuation needed for most musicians.
Another prior art device is taught in U.S. Pat. No. 4,235,144, which includes a contact switch in the guitar pick to determine the exact time the pick strikes the string. This signal is then used to initiate a predetermined effect as well as increment a strike counter that controls an overall variation of a special musical effect. There are, however, several drawbacks to this technique. First, the musician cannot successfully control the effect without striking a string or some other object. Second, the variation in the effect will be coupled only when the string is struck. Third, there is no analog control of the effect parameters.
U.S. Pat. No. 5,300,730 teaches a device that uses strain gauges in the neck and on the guitar pick to control the sound effects. By bending the guitar neck and pick, the musician generates control signals that are used by special effect circuits to modify the electric guitar signal. Unfortunately, the embodiments taught in this patent have several drawbacks. First, one embodiment employs a piezo-electric (PZT) film as a strain gauge. This is problematic because a PZT film is a poor transducer for low frequency or constant signals due to its internal resistance. Further, the PZT film senses the strain of the pick, and the signal generated by forces on the pick is very small. In addition, PZT films are not repeatable with constant forces over time. Finally, PZT films need special signal conditioning circuitry. Another embodiment of this patent suggests using a metal foil strain gauge. However, metal foil strain gauges also produce a relatively low signal level, thus resulting in an unacceptable signal-to-noise ratio. Metal foil strain gauges are also subject to temperature drift and require special signal conditioning circuitry. Moreover, both PZT and metal foil embodiments require extra cabling, and/or wiring, which is very cumbersome for the musician who is recording or practicing, and is unacceptable for a musician performing on a stage.
Thus, there is a need for a simple, low noise, sensitive musical effect controller that a musician can dynamically control without disrupting his or her playing. There is a further need for the effect controller to utilize a sensor that has an adequate frequency response, relatively high signal level, low noise, small temperature drift, requires minimal or no signal conditioning circuitry and no extra cabling, and is easily manufacturable.